Cross line relief mechanism for reversible hydraulic motor



F. H. TENNIS July 13, 1965 CROSS LINE RELIF MECHANISM FOR REVERSIBLE HYDRAULIC MOTOR 2 Sheets-Sheet 1 Filed Oct. l0, 1962 July 13, 1965 F. H. TENNIS 3,194,261

CROSS LINE RELIEF MECHANISM FOR REVERSIBLE HYDRAULIC MOTOR Filed oct. 1o, 1962 2 sheets-sheet 2 e; who www@ a El y Q a@ United States Patent C) 3 194,261 CROSS MNE MECHANlSll/i FR REVERSE-SLE HYDRAULEC MTR Francis H. Tennis, Milwaukee, Wis., assigner to Hydraulic Unit Specialties (lompany, Pen/anime, Wis., a corporation of Wisconsin Filed ct. it), 1%2, Seix No. 229,6tll 3 tClairns. (El. IS7-dill) This invention relates to hydraulic control instrumentalities and refers more particularly to a cross line relief mechanism for a hydraulic system of the type comprising a reversible hydraulic motor and a control valve by which operation of the motor is governed, which cross line rel lief mechanism provides for transfer of hydraulic fluid from one side of the motor to the other when the control valve is in its hold position and there is a lluid pressure difference across the motor which is in excess of a predetermined high value.

A cross line relief mechanism is employed in a hydraulic system wherein a reversible hydraulic motor is connected with a load that tends to exert high inertia forces upon the motor, such as the laterally swinging boom of a large crane, the carriage of a power shovel, or the like. Such a motor is set in motion by shifting a control valve connected therewith to an operating position at which the valve directs pressure lluid from a source thereof to one side of the motor and at the same time permits return fluid from the other side of the motor to flow back to a reservoir or the like. When the control valve is shifted back to its neutral or hold position, it cuts olf the motor from both the pressure fluid source and the reservoir, in effect blocking the lines that connect the motor with the control valve. If the load driven by the motor has high inertia, it tends to keep the motor moving in the direction in which the motor had been driving the load, so that thevmotor tends to push return fluid into one of its lines connected with the control valve an-d to draw a void in the other line.

In the absence of some sort of relief mechanism the motor cannot move when its lines are thus blocked, and the pressure developed in the line into which fluid is being urged by the inertia load could reach dangerously high magnitudes. A cross line relief mechanism prevents this unsafe condition by permitting fluid to bleed from one to the other of the lines connected with the motor when the fluid pressure difference between the lines exceeds a predetermined high value.

The effect of such a cross line relief mechanism is to afford a damped deceleration of the inertia load after the control valve is moved -to its neutral or hold position, due to the throttled flow of fluid from one side of the motor to the other provided for by the cross line relief mechanism.

Heretofore it has been conventional in cross line relief mechanisms to provide two transfer passages through which the two lines or service passages that connected a control valve with its associated motor were communicable with one another, each such transfer passage providing for flow of fluid in only one direction. The reason there had to be a transfer passage for each direction of cross line fluid flow was that communication through each transfer passage was controlled by a more or less conventional high pressure relief valve through which fiuid could liow in only one direction.

ICC

By contrast it is an important object of the present in- Vention to provide a cross line relief mechanism comprising a body having a pair of ports, each connectable with one side of a reversible hydraulic motor, and having only a single relief valve controlled transfer passage through which pressure fluid can llow in either direction, from either body port to the other.

Another object of the present invention is to provide a cross line relief mechanism having a pair of motor ports, a single transfer passage through which fluid can flow in either direction between the motor ports, and a pair of relief valve units, each having poppet mechanism to control communication between one of the motor ports and the transfer passage.

A further object of this invention is to provide a cross line relief mechanism of the character described, which affords unusually smooth and effective deceleration of an inertia load.

Still another object of this invention is to provide a cross line relief mechanism of the character described which can be embodied in an accessory or attachment that is adapted to be secured to the body of a conventional hydraulic control valve of either the integral type or the so-called stacked or sectional type, to adapt such valve for use with a reversible hydraulic motor that drives a high inertia load.

It is also among the objects of this invention to provide a cross line relief mechanism of the character described that can be manufactured easily and inexpensively, can be readily installed in a hydraulic system, and is efficient and dependable in operation.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention, constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FGURE 1 is a sectional view of a cross line relief mechanism embodying the principles of this invention installed, as an accessory or attachment, upon a hydraulic control valve of the sectional type and connected with a double acting hydraulic cylinder, the cross line relief mechanism being shown in an inoperative condition such as obtains when there is no pressure difference across the cylinder; and

FGURE 2 is a fragmentary sectional view on an enlarged scale of the cross line relief mechanism illustrated in FGURE l, shown in its operative condition in which it is relieving a substantially high pressure on the left hand side ofthe cylinder.

Referring now more particularly to the accompanying drawings, the cross line relief mechanism 5 of this invention is shown as embodied in an attachment for one section of a more or less conventional hydraulic control valve 6 of the sectional or stacked type, which valve is connected with a reversible hydraulic motor such as a double acting hydraulic cylinder 'l'. lt will be understood, however, that the Cross line relief mechanism 5 could Y to the .valve body outlet.

equally Well be* incorporated in the body of `the valve itself,- or could be formed as an independent, self-contained unit,y adapted to be mounted at a location apart from` sare', return uid passage means 16 "which opens to an voutlet (not shown), and a pair of motor ports 11i,` each connectable'jbyxrneans including a duct or vline 12 .with oneside of the doubleacting cylinder 7. As is conventional, the valve body k8 isA so formed as to be adapted kfor assembly with' other` similarV bodies thatare connectable with otherhydraulic motors, and with end sections (not shown)V which provide for connection of the open center passage Slw'ith va pump or the .like and of the return iuid passage means ltlftvith 'a reservoiror the' like.v Y

rlfhevalve body 8 hasa bore 13 therein in which a spool or Valve element 14 is slidable in opposite directions froin a neutral "position in which it is shown to either of a pairof operating positions. The` open center passage V9* intersects thespool 'bore 13 intermediate therends thereof ,and is= soV formed that When they spoollld isi, in its neutral position npressure iluid -llowing :in theopen center passage 9 moves througha portion of the spool bore andY When the spoolV isV shifted to onevor the other of its operating positions, however, vit

. blocks the open center passage 9 at the spool bore and 'causes pressure huid tobe diverted to a bridge passage which communicates with :the opencenter passageup-M.

strearrrfrom the spool bore andthe llegs `of which com.

muhicate with the spool bore at zones 16 spaced to opposite sides ofits intersection with the open center passage.

Y encejrnay be Vmade to the@ aforesaid copendingv application;

- 37 is comprised of three ypassage sections, namely a mainV section 137 which extends Vlengthwise between but termi nates short of thej'r'notorport-s,tand 'opposite end secf., tions 237 which connect theendportions ofthe main section V137-/Wit-htl1e.,adjacent motor ports. Each-lof `the Depending upon the operating position in which the spool has been placed, pressure fluid from the bridge passagev 15 `is permitted to flow through another small portion of the spool bore 13 to one or the lotherof a pair of service passagesv 18` whichcommunicate the motor ports 11 with the, spool Vbore at zones 191 of the latter `:spaced axially c outward from its zones 16 of intersection with the legs of the bridge 15. Thus in each operating position of the spool 14'it Vdiverts pressure fluid into the bridge passage 15 and lto a selected side of the double acting cylinder 7 by Way'of one` of the ducts orrlines 12 that connect the .Y

cylinder with the motor `ports 11 in the valve body. At

the. same time, the spool directs return fluid from the .i

motor,.brought to the other motor port 11 by Way of the other line 12, to the return fluid passagemeans L'Which has two branches that intersectthe spool bore near the opposite ends thereof.:

In the present instance .the control `valve is shown as having incorporated :therein anticavitation'means :21,of the'type'disclosed in thecopending application `oFrancis TenhisgfSerial No. 191,163, tiled April 30, 1962, com-y prising a shortpassageZZ connecting each serviceV passage 18 with, its adjacent leg` of the return iiuid passage means 1l); Communication through each of the passages 22 is controlled by lfa check valve 23ofi the type that Vmoves in a direction counter to the direction of lloW that it permits; 'Dhu-s if the spool is in one` of its operating posi-r tions, and if themoto'r, 7 is driven by its load gat arate so rhigh that ,the 'pistoni24 ofthe motor is'evacuating one side of the cylinder 25` faster than hydraulic huid can be I v supplied thereto in the vthe normal manner, a void tends Y to bedrawn in one of theservice passages-18.' The'V check valve 23 adjacent'to that service passage then opensv toV permit additional iiuid to be supplied to the evacuating sideV of the cylinder from'nthe return fluid passagemeans. 10.I

, For further details of the construction and operation of lthis void control oranticavitation mechanismrefer-r.y

It will be apparent that this anticavit-ationfeature is'not required in many installations in .which .a cross line relieff mechanism is'u'tilized, but it doestnot in any Wise; interfere with the cross line relief mechanism 5V or itsoperation. The crosslinerelief mechanism 5 comprises aV body 30 which is adapt-ed tov be jsuitablyI secu-red to Vthe control valve 6, with one fa'ceilll of the body 30 atwise abutting` that face 32 Iofthe control valvebody 8. to` which the;

motor ports 11 open. Extending through the body 30 are service or line passages: 33, which forni continuationsv ,ofv 1 the service Ypassages 18 in the controljyalve body when the two bodies: are assembled with oneA another.;` Each of the servicepassages 33 openslat-one .end yto the'face-31 .of/the body 30,toprovide .'a'cornmunication port 34 that,v4

registers Withzcneofythe.motorports 11 in thev control Valve body.; An O-ring 35 or similar sealgjreceived in an annular groove lopening tothe Vface `31r gof the` body. 30 surrounds eachcomrnunic'atio'n yjportto 'seal thel junction of the two bodies.

port 36 that isfconnectable with one of the;lines or, ducts 12 leading to the doubleacting cylinder.

Fluid vflow betweenVv theV twomotor ports 36,5for cross: line reliehis provided for byv aV singley transfer passage inthe body, generallyfdesignated VIhetransferpassage end lsections 2737"hasra'pair of branches extending at a right angle to one another,` withfone Ybranch i238. normal.

to the `main section'l-37 fand opening to. one end portion thereof through an :annularvalvegseat 38. Y The other.V

branch of p the? end section is provided by.A the line'V passage V373,7which for that purpose'is:"extendedinw-ardly beyond'. K itsport 13e to -thoeobranchjzl andro beinoverlapping re; lation to the adjacent end portiongof the main section 137 vof the transfer passagesk o Y o o A By rneansot the transfer; passznge',` therefore, iluid .transf ferring from one motor port'36 to thegothery must ilovv serially'through` the( .branch passages 238, and .theirv valve seats 38,. Such ltransfertlow :of: tluidfifrom; one, VVmotor* port tothe other is controlled by a'palir of relief-valve yunits 39-mounted on'the body so, that :eachis oooperable VwthY one of thevalvel seats 38.v The; relieflvalve'unitsare of the general type .disclosed and claimed in the copendff ing a'pt'llication kof'fFr'ancisi H.; Tennis; Serial No:v 153,415, f tiled Novernberl?, 196:1, whichifillustratesother embodiments ofsuch; a 'val-ve. unit that arek asiwellsnited for the purpose; asthe .onelillustratedhere; ln'` fact, the'speff cific constructioniandroperatiorr,ofv the .valve unit here shown comprises the subject'ot` asecond copending appli- 'Y .cation of lrancis-H-Tennisl andDfonald BetthlefSerial ."NO. 202,508,fled June T121, 1962;".

Eacho'f the two valve'unitsfl embodiespoppet mech-2 -anisin that ifs Vco'operable"withy its Valve, seat; 3.8 and {which} controlstheew lof liluid through-thebranch' passage,.23%V vlcatling through-the seat'; Moreover,= thepoppet mech? anism of eachvalve unit is of the type-:tha-topfens inare lspense toV pressuresofltwoodifferentpredetermined v'alu'es;V riamely a hig'hvalue 'andaflowrvaluegve VForthis"purpose,. p

each l valve unit comprises an louter:poppetin'enitberv 42 )vhich yisaxially slidable back and forth ina cup-lik'ejcas? 'ing 40 having its rim {portioh screwgthreaded into a ksuitablytapped holeinthe body openinginto b'ne'end portion of the main section E137 of the transferV passagefatfa loca# non certainty Qppesitegtiie iadjscentvaive restes. 1 p Vfrire ,outer poppet fmember "42 proj ectsldownwardly Vout i of l the open endiof thepcasirlgttl mtoftheo-rna-in section V137 I"of the 'transfer passagegfand itsl'rfroritend opposes and engages Y the valve seat-,38 `beneathjitato normally"blocl uiddow throughrthe branch passagejrZSSjleading downwardly frontV l Vsaid seat. Thercasing: 46j is fojrrnejd .with'a Vcoaxial inner At"` its-other end each linerpassage Y opens to. another` sidei of the body 30 ata motorfor. line tubular member and a spning seat member 56 which is axially adjustably threaded into the outer end of the casing.

The cylindrical side wall 41 of the casing surrounds the outer poppet member d2 with substantial clearance to dene an annular passage 4l around said poppet member.

The inner tubular member 52 extends forwardly into a rearwardly opening counterbore 53 in the outer poppet, and cooperates with the latter to define a pressure charnber 45 adjacent to the bottom of the counterbore 53. The front portion of the inner tubular member and the cylindrical skirt 44 on the rear of the outer poppet thus comprise a cylinder and piston, but it will be noted that in this instance the usual relationship is reversed, in that the outer poppet member, which as the movable element can be considered the piston, surrounds the inner tubular member which is fixed and may therefore be considered i the cylinder.

A coaxial bore 46 that extends through the front portion of the outer poppet member provides for communicating the pressure chamber 45 with what might be termed the system port provided by the adjacent branch 23S of the transfer passage, Hence pressure of fluid in the chamber 45 is normally the same as that of fluid in the system port and at the motor port with which it communicates via the service passage 33. lt should be noted that the valve seat 33 has a somewhat smal-ler diameter than that of pressure chamber 45, and hence the fluid in that chamber tends to maintain the outer poppet member engaged with the seat 38, against the tendency of pressure fluid acting upon the front of the outer poppet member through the seat 3S to move the poppet member off of its seat.

The front end portion 43 of the outer poppet member is shown reduced to a diameter less than the inside diameter of its skirt 44, so as to define a forwardly facing annular surface 49 which -is spaced behind its seat engaging surface, and upon which pressure of fluid in the main section 137 of the transfer passage is manifested. F[he effective area of the surface 49, of course, is somewhat greater than the c-ross sectional area of the skirt i4 on the rear of the outer poppet member. Hence Whenever pressure of fluid in the main section 137 of the transfer passage is at a value above that of fluid in the system port 233 of each valve unit, the fluid in the main section of the transfer passage acts upon the surface 49 of the outer poppet member of the valve unit to cause the poppet mechanism to open the branch or system port 23d and thus communicate the main section L37 of the transfer passage with the motor port associated with said port 238.

The poppet mechanism of each valve unit also includes an inner or pilot poppet 50 which is adapted to open in response to substantially high pressure in the associated line passage 33 or system port 233, and which, when so opened, effects opening of the passage 238 to the main section lr37 of the transfer passage, in this case by causing unseating of the outer poppet member 42.

The seat Si with which the pilot poppet cooperates is formed in the inner tubular member 52 by a portion thereof, spaced behind its front end, that has a reduced inside diameter. The valve element on the pilot poppet that engages this seat comprises an enlarged head 54, the

rear face of which serves as a seat for a coiled compression spring 55 by which the pilot poppet is biased .forwardly to its seated position. The rear end of the spring 55 reacts against the adjustabler spring seat member 5d, and the spring is held concentric with the pilot poppet by a rearwardly extending stem portion 57 on the pilot poppet which extends through the convolutions of the spring and is guidingly received in a forwardly opening well 5S in the adjustable spring seat member 56. y It will be apparent that the force which the spring 55 exerts upon the pilot poppet, as determined by the axial position of adjustment of the spring seat member Se, controls the value of duid pressure in the chamber 45 at which the pilot poppet is unseated. An acorn nut 59 threaded onto the projecting outer end portion of the spring seat member cooperates with another nut dll to lock the spring seat member against inadvertent rotation and to provide a duid tight seal.

Opening or unseating of the pilot poppet permits iiuid to flow rearwardly out of the pressure chamber 45 through the seat 5l, and through radial bores 5l in the inner tubular member, spaced behind the seat 5l; thence around the rear of the main poppet member and forwardly into the main section 137 of the transfer passage, through the annular passage dl provided by the clearance space between the outer tubular member and the outer poppet member. At the same time, flow of fluid from the system port 23S and the line passage 33 into the chamber i5 is restricted to a rate slower than that at which fluid exhausts from chamber 45 through the pilot poppet seat, by a flow restricting plunger 6l and the outer poppet therefore moves away from its seat 38 in response to the force which lluid in the system port 233 exerts upon the front end of the outer poppet 42.

The iiow restricting plunger el is an elongated tubular member which is freely slidable in the bore 46 in the front of the main poppet member, with a small clearance, so as to move rearwardly in response to the rearward flow of fluid through said bore When the pilot poppet opens. Extending coaxially forwardly from the valve element 5d of the pilot is a conical projection 63 which is adapted to be partway received in the rear end of the tubular plunger 6l when the latter is in its rearmost position, to substantially close the rear of the tubular plunger while allowing restricted liow from passage 33 to the chamber d5 through the clearance space between the plunger 6l and the bore le in the front of the outer poppet. lt will be apparent, however, that pressure of uid in the service passage 33 and hence the system port 238 is manifested upon the front end of the plunger 61 and is transmitted by the plunger to the pilot poppet to aid in holding the latter unseated until pressure in the service passage drops back down below its predetermined relief value.

it will be appreciated that the coaction of the pilot poppet and the flow restricting plunger 6l assures smoot chatterfree unloading action of the valve mechanism 39, prevents it from cracking before pressure in the line passage reaches the relief value for which it is adjusted, and enables it to close promptly when such pressure drops back down below the predetermined relief value.

When the pilot poppet is closed the tubular plunger 6l remains in a forward position in which a circumferential flange 64 thereon near its rear end engages the bottom d5 of the counterbore in the outer poppet member. T he plunger 61 is lightly biased to this normal forward position, in which its rear end is spaced from the projection 63 on the pilot poppet, by means of a small coiled compression spring 68 which reacts between the flange 6don the plunger 6l and the inner tubular member 52. In this normal position of the plunger 6l, which it of course maintains when the valve mechanism opens in response to a rise in pressure in the main section 37 of the transfer passage 37 to a value above that obtaining in the system port 23S, said plunger permits substantially unrestricted ilow of fluid between the pressure chamber d5 and the system port 238.

The operation of the cross line relief mechanism of this invention will now be apparent and can be briefly summarized as follows. Assume that the spool lli of the control valve 6 is shifted to its left hand operating position, causing pressure duid to be diverted to the right hand side of the cylinder Z5 so as to actnate the motor 7 and a load L connected therewith to the left. If the valve spool is now abruptly returned to its neutral or hold position shown in FIGURE l, the inertia of the load tends to keep the piston 24 of the hydraulic motor moving toward the left, imposing upon the left handtline 12 a fluid pressure which might be dangerously high Yif not relieved, andtending to draw a void in the 'right hand line 12.

The high iluidpressure in theleft hand linefpassage V331 and systemport. 238,:Which connect with theleftV hand duct 12, isrlikewise manifestedY in kthe pressure chamber 45 of theV left handvalve mechanism 39 due to the communication of said pressure-chamberfgwith thev left hand line passage through the bore :of the tubular plunger 61, Assuming that this fluid pressure is of suciently large magnitude to unseat the pilotpoppet, Vthe opening of lthe pilot poppet-permits fluid to exhaust from f the pressurey chamber 45 of the leftnhand valve mech-v anism, through the pilot valve seat, around the` rear of of the `transfer passage.

plug-like projection 63 onnthe pilot poppet to restrict the flow` of fluid fronrthe left hand line passage 33 iinto ther chamber 45, andthe outer poppet-will move off of its:`

seat inresponse to theV force which fluid in the system port 238 exerts upon its front end,'to permit uid tov left hand valve mechanism.`

-It will be appreciated, of course, that whenever the.

.V the .outer poppet member, and into the main section 13,'7y

When such flowv of Vfluid throughv I the pilot valve seat 51 `Vbegins, the -tubular plunger :.61 will be carried rearwardly into engagement with g thev z pressure rises toV an abnormally high value in thelefthand Y line passage duetto theinertia of the load, as mentioned hereinbefore, there .will be a correspondingpressure de'- crease in 'the right hand line passageand danger of drawing a void in the right handline 12. Hence, at the:-

time fluid at such abnormally high ipressure in theleft hand line .passage is relieved into the rnain'sectionfofV the transfer passage, the pressure of .fluid in Vthe 'right` hand linepassage will .have'decreased by an amount line passage, and this decreasefisv likewise -smanifested in the pressure 'chamber'. of therighthand valve mechanism. Consequently, as soon as fluid at increased pressure in the main section 137 of the transfer passage.l

exceeds Vthat of uid atV decreased pressure in the right hand line-passage, the outer poppet; member ofthe right hand valve `mechanism moves rearwardly oif of its vseaty in response to the force which fluidin the main section of the transfer passagefexerts'upon theforwardly facing surface 49 of thev outer pbppet. Thus both valve mech- '40 f proportional to the increase in pressure in .the left hand I- anisrns .will be promptlyvopened to' permit ow of fluidv fromv the left hand Yline relief value setting of the left handvalve mechanism 39,'

Obviously if the :direction of `motion of theinertia]A loadwere reversed, the mechanism 0fthisinvention would i Y similarly permit cross line relief flowy of yfluid from the right hand line passage to the lefthand one- Y passage into the right hand 1' linepassage through the transfer passage until Vsuch times,

Y as pressure in the left hand `lin'epassage drops below the; -55' ports S4 would` be eliminated andthe motor ports 36 of the; i

mechanism wouldbe .connected `with the cylinder .sepa-,

rateiy from butin parallel with the connections to the control valve 6.

From the foregoing description .taken together with the.;v

accompanyingdrawings it will .be apparent. that this inf vention provides a Cross,` linelrelief mechanism forfa re- ;versible hydraulic motora/herein a singletransfer. passage wherein flow' of u'id through said transfer passage. is con- Y combination of: Y i Y v (A) a bodyhaving a pair offline-passages adapted for Y trolledby'a pair Vof combinedhigh pressurefrelief andvoid control valves which 4assure stable, chatterffreeoperation of thecross line Vrelief mechanism and provide for'smoothl deceleration of; the

mechanism; j v Y What is claimed as myrinventiongis': t

hydraulic :motor-.connected 'with `the 1. In a hydraulic control instrumentality 'vofftlzneytype'-Y comprisinga -bodyhaving' a .pair of linepassageseach coni Y, nectable withone side :of 'fa reversiblehydraulic;motor,V .cross line relief means'k for transferringhydraulicpressure. fluid from either line passage in which'an abnormally high pressure developstoi-the otherrlineipassage,v comprising: e

e (A) a transfer passagein the' body.to1communicate;the

line passages `withione another andconne'cting lonly" therewith;. 4 Y *Y ,(B) annulanvalveseatslin the transfer passage,one-f0r each Yline passage,vv spaced fromone.anotherralongfthe vlength Vof the' transfe,r1-passage. and eachV ,deiin-ingla connectingpassageV through which itsline passage is communicable with ,the transfer passage, vsaid. valve y seats `facing fin ;the direction lthat, iluido'ws .therethroughfrom the .line passages-tothe transfer pas Y sage; Y

(C)A and la bi-directionalV valve unit mounted-y ingthe'.

'body at a location opposite each ,t valve seat,l andVv Vwholly outsideV its line passage, said :fvalv'e units. comprising -Y (l) puppet means'in each .valve unit projecting forwardly] .therefrom `into the transfer passagetoward'. itsvalveseat for-cooperation .therewith and ing passage dened thereby',kr e Y (2) means* in eachvalve unit responsive to presf sure -of iluidat an ,abnormally high value inwits line passage fory effecting rearward .actuation of `itspoppet means; to'establish relieflowof huid throughV its' Vconnecting passage to the., transfer passage, 1 Y

transfer'V passage .to hou/through itsy connecting passage to the associated line passage,

2. A. hydrauliccontrol `instrumentality comprising the connection with the Opposite sides yof: a reversible uid motor; Y f Y therewith; I (C) f annular valve seats sages;

fseatyl Y. posits their respectivevalve seats; 1 Y l (F) l onefof saidvalve-mechanisms,comprising rahigh* pressure relief Vvalvewhich projeets forwardly intthje transfer passage for engagement withitsf valve seat., andwhich Opens in response to; pressure of fluid at .an abnormally. high value in vits linespassag'e; t establish' relieffflowof such fluid tothetransfer passage;

Y its Vseatzandfwhich is/'caused to opensolely in response (B) a transfervpassagejin :thebody connectingsaid linev passages; Iwith one another and .communicating only( imthe transferipassaggfone for each'line passage,u"through *which.the-lattercareconvy Y' `rnuncated withxthe transfer passage, {said'` seats 'being'. 7 spaced from one ;,anotheragalong the "length `of .the

:transfer passage and facing away; from' :theiri lineV pas- (D) a pair; of valve 'jmecha'ni'svms,onfelfforeachfvalvek y As indicated earlier, the cross line relielE mechanisms 6 l v of Vthis invention may be employed ina hydraulic circuit apart frornthe control valve thereof, in whichV case the X .'(E) meansrnountingthevalve Ameclia'nisirisinthebordy at locationswholly;outsidethe linexpassag'es andgop-I to the pressure. ofsaid relief iuid'inthetransfer, pas-l:

9 l@ sage at times when the relief valve opens, so as to thus which an abnormally high pressure obtains to flow through permit pressure fluid to ow serially through both the transfer passage to the other line passage.

valve seats from the line passage associated with said relief valve to that associated with the check valve, References Cited by the Examiner said check valve opening in a direction counter to 5 UNITED STATES PATENTS such flow of relief fluid through its seat so as not to x obstruct such flow to its associated line passage. 2954011 9/60 Krehblel 91-437 "i 2,989,072 6/61 Banker 137-491 3. The hydraulic control instrumentality of claim 2, wherein each of the valve mechanisms comprises a high pressure relief valve as Well as a reverse acting check valve, 10 WILLIAM F O DEA Prmmry Exammer' so as to enable pressure fluid from either line passage in M. CARY NELSON, Examiner. 

1. IN A HYDRAULIC CONTROL INSTRUMENTALITY OF THE TYPE COMPRISING A BODY HAVING A PAIR OF LINE PASSAGES EACH CONNECTABLE WITH ONE SIDE OF A REVERSIBLE HYDRAULIC MOTOR, CROSS LINE RELIEF MEANS FOR TRANSFERRING HYDRAULIC PRESSURE FLUID FROM EITHER LINE PASSAGE IN WHICH AN ABNORMALLY HIGH PRESSURE DEVELOPS TO THE OTHER LINE PASSAGE, COMPRISING: (A) A TRANSFER PASSAGE IN THE BODY TO COMMUNICATE THE LINE PASSAGES WITH ONE ANOTHER AND CONNECTING ONLY THEREWITH; (B) ANNULAR VALVE SEATS IN THE TRANSFER PASSAGE, ONE FOR EACH LINE PASSAGE, SPACED FROM ONE ANOTHER ALONG THE LENGTH OF THE TRANSFER PASSAGE AND EACH DEFINING A CONNECTING PASSAGE THROUGH WHICH ITS LINE PASSAGE IS COMMUNICABLE WITH THE TRANSFER PASSAGE, SAID VALVE SEATS FACING IN THE DIRECTION THAT FLUID FLOWS THERETHROUGH FROM THE LINE PASSAGES TO THE TRANSFER PASSAGE; (C) AND A BI-DIRECTIONAL VALVE UNIT MOUNTED IN THE BODY AT A LOCATION OPPOSITE EACH VALVE SEAT, AND WHOLLY OUTSIDE ITS LINE PASSAGE, SAID VALVE UNITS COMPRISING (1) POPPET MEANS IN EACH VALVE UNIT PROJECTING FORWARDLY THEREFROM INTO THE TRANSFER PASSAGE TOWARD ITS VALVE SEAT FOR COOPERATION THEREWITH AND TO NORMALLY BLOCK FLUID FLOW THROUGH THE CONNECT-/ ING PASSAGE DEFINED THEREBY, (2) MEANS IN EACH VALVE UNIT RESPONSIVE TO PRESSURE OF FLUID AT AN ABNORMALLY HIGH VALUE IN ITS LINE PASSAGE FOR EFFECTING REARWARD ACTUATION OF ITS POPPET MEANS TO ESTABLISH RELIEF FLOW OF FLUID THROUGH ITS CONNECTING PASSAGE TO THE TRANSFER PASSAGE, (3) AND MEANS IN EACH VALVE UNIT RESPONSIVE SOLELY TO THE PRESSURE OF SUCH RELIEF FLUID IN THE TRANSFER PASSAGE FOR EFFECTING REARWARD ACTUATION OF ITS POPPET MEANS TO ENABLE SUCH RELIEF FLUID IN THE TRANSFER PASSAGE TO FLOW THROUGH ITS CONNECTING PASSAGE TO THE ASSOCIATED LINE PASSAGE. 